Literaturdatenbank
Literaturdatenbank |
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Spencer, R.-J., Janzen, F. J., & Thompson, M. B. (2005). Response of juvenile growth rate to experimental removal of nest predators in a long-lived vertebrate. Ecology, (under review, different version published 2006).
Added by: Sarina Wunderlich (27 Mar 2011 16:16:49 UTC) |
| Resource type: Journal Article BibTeX citation key: Spencer2005a View all bibliographic details  |
Categories: General Keywords: Australien = Australia, Chelidae, Emydura, Emydura macquarii, Fressfeinde = predators, Habitat = habitat, Schildkröten = turtles + tortoises Creators: Janzen, Spencer, Thompson Collection: Ecology |
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| URLs http://emydura.50m ... avorite_links1.htm |
| Abstract |
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Emydura macquarii Examining the phenotypic and genetic underpinnings of life-history variation in long-lived organisms is central to the study of life-history evolution. Juvenile growth and survival are often densitydependent in reptiles and theory predicts the evolution of slow growth in response to low resources (resource-limiting hypothesis), such as under densely populated conditions. However, rapid growth is predicted when exceeding some critical body size reduces the risk of mortality (mortality hypothesis). Here we present results of paired large-scale, 5-year field experiments to identify causes of variation in individual growth and survival rates of an Australian turtle prior to maturity. To distinguish between these competing hypotheses, we reduced nest predators in two populations (retained a control population) to create variation in juvenile density by altering recruitment levels. We also conducted a complementary split-clutch field transplant experiment to explore the impact of incubation temperature (25C or 30C), nest predator level (low or high) and clutch on juvenile growth and survival. Juveniles in high-density populations were not resource limited, growing more rapidly than young turtles in the control populations. Our experiments also revealed a remarkably long-term impact of the thermal conditions experienced during embryonic development on growth of turtles prior to maturity. Moreover, this thermal effect was manifested in turtles approaching maturity rather than in turtles closer to hatching, and was dependent on the population density in the post-hatching rearing environment. This apparent phenotypic plasticity in growth is complemented by our observation of a strong, positive genetic correlation between individual growth in the experimental and control populations (rG = >+0.77). Thus, these Australian pleurodiran turtle populations have the impressive capacity to acclimatize plastically to major demographic perturbations, as well as enjoy the longer-term potential to evolve adaptively. These findings suggest that long-lived organisms possess two means for responding to substantial changes to population structure to maintain viability.
Added by: Sarina Wunderlich |